In an imaging device, such as a digital still camera, different types of photographic light are needed during or prior to capturing an image of a scene of interest, such as a flash of light and an autofocus auxiliary light. Typically, separate lighting devices are used to provide these different types of photographic light. The most common lighting devices include electronic flashes and autofocus light devices.
Electronic flashes provide flashes of light to enhance images captured by a digital still camera or other imaging devices. Traditional electronic flashes utilize a bulb filled with gas, such as argon, krypton, neon and xenon, or vapor, such as mercury vapor. When a high voltage is applied to the bulb, the gas or vapor is ionized, allowing electrons to flow through the gas or vapor. These electrons excite the atoms of the gas or vapor, which emit light. The wavelength characteristics of the emitted light depends on the gas or vapor in the bulb. In the case of mercury vapor, the emitted light is ultraviolet light, which is usually converted to visible light using fluorescent material since ultraviolet light is typically not desired.
Recently, light emitting diode (“LEDs”) have been improved to a point with respect to operating efficiency where LEDs are now replacing conventional light sources, even bulbs in electronic flashes. Existing LEDs can emit light in the ultraviolet (“UV”), visible or infrared (“IR”) wavelength range. These LEDs generally have narrow emission spectrum (approximately +/−10 nm). As an example, a blue InGaN LED may generate light with wavelength of 470 nm +/−10 nm. As another example, a green InGaN LED may generate light with wavelength of 510 nm+/−10 nm. As another example, a red AlInGaP LED may generate light with wavelength of 630 nm+/−10 nm. However, since electronic flashes typically need to produce white light for color rendering purposes, different color LEDs such as red, blue and green LEDs are used together in an electronic flash to produce white light.
Autofocus light devices provide autofocus auxiliary light, which is a bright light with a narrow view angle. The autofocus auxiliary light is used measure the distance of a subject being photographed, such as a person, for autofocusing. Currently, many autofocus light devices in digital still cameras use an LED as the light source.
The electronic flash and the autofocus light device consume a significant amount of space in a digital still camera, especially in a compact digital still camera. Thus, the electronic flash and the autofocus light device hinder the development of a very compact digital still camera.
In view of this concern, there is a need for a system and method for providing different types of photographic light in an imaging device, such as a digital still camera, that does not require a significant amount of space in the imaging device.